By modifying habitats and creating bridges and barriers between landmasses,
climate change and tectonic events are believedto have important
consequences for diversification of terrestrialorganisms. Such
consequences should be most evident in phylogenetichistories of
groups that are ancient, widespread, and diverse.The squirrel family
(Sciuridae) is one of very few mammalian familiesendemic to Eurasia,
Africa, and North and South America and isideal for examining these
issues. Through phylogenetic and molecular-clockanalyses, we infer
that arrival and diversification of squirrelsin Africa, on Sunda
Shelf islands, across Beringea, and acrossthe Panamanian isthmus
coincide in timing and location with multiplewell-documented
sea-level, tectonic, and paleontological events.These precise
correspondences point to an important role for globalchange in the
diversification of a major group of mammals.